Why should there be extra effort for online classes?
My university had a course where an external professor would deliver a mixed online/offline course. Videos were available on institute website. Professor would hold a class every week to go through that week's contents and clarify student doubts.
This saved a ton of effort on the professor's part.
There is a reserved scheduled class room for the class, but there is no organized zoom meeting yet (or maybe not use zoom after all?).
There is a mail box to drop of home work assignments, but nobody has figured out where students should email things for grading (the prof, the TA or a function account?).
The prof has a set of notes that (s)he writes onto the white board, but not a set of slides to be emailed out. Or might have electronic slides, but they contain annotation that should not be sent out to students.
Everybody has to figure out how to make sure that 200 students can join the zoom session, but have their mic muted. And know how to unmute when they want to ask a question.
Exams for the mid terms might be printed but now need to be (e)mailed. And how do you prevent cheating in an exam that was meant to be taken under supervision with pen(cil) and paper only. Of course you can create an open-book exam where google doesn't help, but that is extra effort. And does not prevent collusion between students.
Somebody need to figure out how to replace lab courses.
And the list goes on. All of that can be fixed. And after a couple of semesters an online class might be no more (or possibly even less, but that is not proven) work than the current offline course. But switching in the middle of a semester with ideally no downtime IS a lot of extra effort.
The lab courses and to a somewhat lesser degree seminar-type classes are the really tough question. A course like 2.007 [1] which is one of the best known and most useful classes in the Mech Eng curriculum can't be replicated online to any meaningful degree--especially with zero notice and planning.
I'm honestly not sure what you do at this point. Finish up the semester as best you can and just give everyone a Pass? Force people to attend a summer session whether or not they can afford to not be working? There aren't any good options.
For one thing, profs often teach some classes repeatedly, which means they dont have to put substantial effort into planning for subsequent offerings. If the planned content is somehow unsuitable for a different medium of delivery, this would take some planning that they weren't expecting at the beginning of the semester.
My university had a course where an external professor would deliver a mixed online/offline course. Videos were available on institute website. Professor would hold a class every week to go through that week's contents and clarify student doubts.
This saved a ton of effort on the professor's part.